牛における射精反射機構の神経解剖学的研究

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The mechanism of ejaculatory reflexes is characteristic in bulls as reported by previous workers. Wilcox and coworkers reported that about 10% of the culled bulls were due to the difficulty of semen collection. For the resolution of the problem and to improve the efficiency of semen collection, the mechanisms of ejaculatory reflexes in this species should be clarified neuro-anatomically. At the present study the effects of auditory, olfactory and visual stimuli concerned with the cerebral cortex on the sexual drive and on the ejaculatory reflex were systematically investigated. Then, a location where the terminal nerve receptors involved in ejaculation existed was peripherally demonstrated. Furthermore a silver impregnation method was devised to stain the peripheral nerves of the bull penis. With this method, the author made clear the sensory nerve endings, the nerve supply and the nerve development of the bull penis. The results are summarized as follows. I. Studies on the effects of stimuli concerned with the cerebral cortex on the mechanisms of ejaculatory reflexes. 1. Auditory stimuli from the specific calls of cow significantly reduced sexual reaction time (P <0.01), but these were not effective for the semen characteristics. 2. Auditory stimuli from the noises of tractor (about 85 phon) significantly inhibited the sexual reaction (P <0.05), but these were not effective for the semen characteristics. 3. Auditory stimuli from shouting caused delay in sexual reaction time (P <0.01). However in some cases these auditory stimuli reduced the reaction time for the first ejaculation (P <0.01). 4. The olfactory stimuli from the mucus or urine of the estrous cow elicited sexual drive in some bulls, but did not in most other bulls. 5. The mucus of the estrous cow reduced sexual reaction time in some bulls, but did not in the majority of the bulls. 6. It was demonstrated that visual stimuli were highly effective for a sexual reaction including ejaculation. The relationship between sexual reaction time and semen characteristics is analyzed and classified to the following three types. 1) Type I : Bulls showing significant positive correlation between both parameters, i.e., a longer reaction time resulted in larger volume of semen. This type of bulls was most popular. 2) Type II : Bulls showing no significant correlation between both parameters, i.e., semen volume was not influenced by the reaction time. 3) Type III : Bulls showing negatively significant correlation between both parameters, i.e., a longer reaction time resulted in smaller volume of semen and inferior semen quality. This type of bulls was more sensitive especially to the visual stimuli than other type of bulls. Excessive visual stimuli to these bulls by restraining or false mounting were not favorable at the semen collection barn, because they had already been in the sexual preparatory process on the way to the collection barn from their pens. II. Studies on the localization of the sensory nerve endings which induce ejaculation. 1. The galea glandis of the bull did not contact with anything during masturbation, but a bull usually rubbed his erected penis with his dewlap at the portion of the collum glandis or at the more proximal part of the penis. This suggests that the sensory nerve endings locate at the collum glandis. 2. When a massage on the galea glandis or on the prepenile sheath was applied the bull did not cause ejaculation. The semen was obtained by massaging the collum glandis, but in this case, the massage might have been applied simultaneously on the penile sheath. 3. Ejaculation did not occur when the inner temperature of artificial vagina was at 18℃, but the semen was successfully obtained at 40℃. This suggests that the temperature also plays an important role on eliciting ejaculation. 4. Anesthesia on the surface of galea glandis with Lidocaine did not block the ejaculatory reflex. On the other hand, ejaculation did not occur when this case
石川県農業短期大学の論文
1980-12-25

著者

泉徳和
石川県農業短期大学・生物生産学科・家畜繁殖学

牛における射精反射機構の神経解剖学的研究

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